Currently, as a core technology of a transport network, an optical transport network (OTN) technology includes electrical-layer and optical-layer technical specifications, and features diverse operation, administration, and maintenance (OAM) functions, a powerful tandem connection monitoring (TCM) capability, and a powerful out-of-band forward error correction (FEC) capability. This can implement flexible scheduling and management for large-capacity services.
As shown in FIG. 1, an OTN frame is a 4080×4 modular structure, and includes a frame alignment signal (FAS), providing a frame synchronization function. OTUk OH is an overhead byte of an optical channel transport unit (OTU), and provides a network management function at an OTU level. ODUk OH is an overhead byte of an optical channel data unit (ODU), and provides maintenance and operation functions. OPUk OH is an overhead byte of an optical channel payload unit (OPU), and provides a customer signal adaptation function. OPUk payload is the OPU, and provides a customer signal bearer function. FEC is a FEC byte, and provides error detection and error correction functions. The coefficient k represents a supported bit rate and different types of OPUks, ODUks, and OTUks. If k=1, it indicates that a bit rate level is 2.5 gigabits per second (Gbit/s), if k=2, it indicates that a bit rate level is 10 Gbit/s, if k=3, it indicates that a bit rate level is 40 Gbit/s, if k=4, it indicates that a bit rate level is 100 Gbit/s, and if k=flex, it indicates that a bit rate is arbitrary.
An OTN may be used to transparently transmit various communications services. A packet service is a typical one in the various communications services. In the packet service, a service is transmitted using a packet. A length of each packet is variable, and an idle character usually exists between adjacent packets. A quantity of idle characters is also variable.
Currently, for transmission of a packet service, the OTN usually uses a Generic Framing Procedure (GFP) mapping manner. In this manner, the packet service is first encapsulated into a GFP frame, and then the GFP frame is mapped to an OPU payload area. As a rate increases, problems inherent in this mapping manner gradually emerge: (1) A byte-granularity mapping manner is used in the GFP. As the rate rapidly increases, if a byte granularity is still used for GFP mapping encapsulation, implementation complexity is greatly increased. (2) Because a GFP frame generated during GFP mapping processing has an unfixed frame length, a position in which a GFP frame header may appear needs to be identified more frequently. In addition, data in each clock cycle is differently processed. This further increases complexity of customer service mapping processing performed at a high rate and a large bit width. (3) Because a GFP core head (core frame header), a Payload head (payload frame header), a frame check sequence (FCS), and the like are added to the GFP frame generated during the GFP mapping processing, bandwidth utilization is lowered.